This invention generally relates to electric incandescent lamps and has particular reference to an improved filament mount assembly for such lamps, and to a novel method of manufacturing the mount assemblies.
One of the critical problems encountered in the production of incandescent lamps involves the mounting of the coiled filament within the envelope and its attachment to the lead-in conductors. In large type incandescent lamps, this is generally achieved by sealing a glass stem to a pair of lead wires and forming the ends of the leads into clamps that are closed around the ends of the filament coil. Various other means for attaching the filament to the lead wires have also been employed down through the years. For example, U.S. Pat. No. 1,046,785 to Henderson discloses a lamp in which ends of the filament are secured to the lead wires by forming the ends of the wires into short helices or tubes that are attached to the filament by fusing or pasting the members together. In accordance with U.S. Pat. No. 768,173 (Fanta) the ends of the lamp filament are fastened to tubular metal tips which in turn, are inserted into and secured to metal sleeves that are attached to the inner ends of the platinum lead wires. The use of several interfitted tubular members to fasten the lead wires of an incandescent lamp to a filament is also disclosed in U.S. Pat. No. 2,398,969 to Singer. A fluorine-containing incandescent lamp having lead wires with end portions that are drilled to provide tubular cavities which receive the ends of a tungsten filament and protect them from attack by the fluorine additive is disclosed in U.S. Pat. No. 3,263,113 to Schroder.
The filament mounting operation is even more complicated in the case of automotive sealed-beam type lamps where one or a pair of coiled filaments must not only be fastened to the lead wires but accurately positioned relative to one another and the focal point of the reflector in a very confined space in order to provide the proper high-beam and low-beam light patterns. A sealed-beam type incandescent lamp in which accurate placement of a pair of coiled filaments within the reflector component of the envelope is achieved by clamping a short auxiliary lead wire to each of the filament legs and then inserting such auxiliary leads into notched ends of the main lead-in wires and welding them in place is disclosed in U.S. Pat. No. 3,513,347 to Murray et al. The use of metal sleeve components to facilitate the attachment of the filament legs to the lead-in wires of an incandescent lamp is also generally known in the art and is disclosed in U.S. Pat. No. 3,854,180 to Pastijn et al. In accordance with the patented method, the filament leg is inserted into a cylindrical metal sleeve which is positioned in transverse relationship with the lead wire and the sleeve is then compressively deformed and simultaneously spot welded to both the lead wire and the filament leg.